Abatacept (marketed under the trade name ORENCIA® in both the United States and Europe) is a genetically engineered fusion protein composed of a modified Fc region of the immunoglobulin IgG1 fused to the extracellular domain of cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4). Abatacept has an approximate molecular weight of 92,300 Daltons, as determined by mass spectrometry, and has a binding affinity for CD80 of approximately 6.5 nM and for CD86 of approximately 14 nM (see, Larsen et al., American Journal of Transplantation, 5:443-453 (2005)).
Abatacept is produced by mammalian cell (Chinese Hamster Ovary) culture in a nutrient medium. For intravenous administration, abatacept is supplied as a 250 mg lyophilized powder in single-use vial for reconstitution with 10 mL of sterile water. The reconstituted abatacept solution is further diluted to 100 mL by replacing a volume of 0.9% Sodium Chloride Injection, USP, with an equal volume of reconstituted abatacept solution, as required for a patient dose (see ORENCIA® Product Label). For subcutaneous administration, abatacept is supplied as a 125 mg/mL single-dose prefilled glass syringe.